Current Issue : October - December Volume : 2011 Issue Number : 1 Articles : 5 Articles
Possible base sliding induced by an earthquake on concrete gravity dams is obtained by a simplified procedure. The model is a nonlinear single-degree-of-freedom system which takes into account dam-water-foundation interaction based on the model developed by Fenves and Chopra (1987). The nonlinearity is in the foundation rock, since a threshold value for the sliding foundation resistance, modeled with the Mohr-Coulomb yielding criterion including a frictional and a cohesive component, is imposed. Nonlinear step by dams is obtained by a simplified procedure. The model is a nonlinear single-degree-of-freedom system which takes into account dam-water-foundation interaction based on the model developed by Fenves and Chopra (1987). The nonlinearity is in the foundation rock, since a threshold value for the sliding foundation resistance, modeled with the Mohr-Coulomb yielding criterion including a frictional and a cohesive component, is imposed. Nonlinear step by step dynamic analyses are carried out on four case studies representing typical examples of Italian concrete gravity dams by utilizing several natural earthquakes. On the basis of the obtained results, a simplified methodology to estimate residual displacement without performing nonlinear dynamic analysis is presented. An example of application using as seismic input the elastic response spectra furnished by the Italian Code is also presented....
This experimental study was carried out in two test series to investigate the feasibility of decreasing the water content and increasing the shear strength and axial load capacity of laboratory-prepared soft clay by electrokinetic treatment. The focus of the investigations is the influence of pore fluid chemistry (fresh or highly saline water) on the gained improvement and on the energy consumption. The results showed that electrokinetics was effective in improving the properties of the soft clay with fresh and saline water. The degree of improvement, however, was superior in tests with freshwaters along with a lower energy consumption. The minimum water content and the maximum shear strength after the treatment were reported near the anode (28% �± 3.6 and 99.3?kPa �± 15.4 compared to 49.7% �± 3.1 and 12.1?kPa �± 1.7 in the control). The maximum axial load capacity of the foundation model after the treatment was 416?N compared to 28?N in the control. The energy consumption varied between 69.1 and 1994.6?Whr....
Investigations carried out to study the effect of Cr (VI) (1000ââ?¬â??3000?mg/l) on solidification and hydration behavior of Ordinary Portland cement (OPC) and rice husk ash (RHA) blended (10%, 20%, and 30%) cement show that addition of RHA accelerates final setting as compared to control samples (OPC) and retardation in setting time has been observed on increase in rice husk ash concentration (10%ââ?¬â??30%). Solidification studies show that the compressive strength of controls and rice husk ash blended samples increases with increase in the curing period and maximum strength was observed with 20% RHA blended samples. With the increase in Cr (VI) concentrations, the strength of OPC and RHA blended samples decreases as compared to controls (without chromium). The results of Toxicity Characteristics Leaching Procedure (TCLP) test, (pH?3), show that the retention capacity of OPC and RHA blended samples was in the range of 92% to 99% and the leached Cr (VI) concentration was under the allowable limit (5?mg/l) of U.S. EPA. The chemistry of influence of Cr (VI) on hydration of cement was examined by X-ray diffraction which shows the formation of various crystalline phases during solidification in rice hush ash blended cement....
This paper presents the results of effect of inclusion of water, sodium hydroxide and carbon tetrachloride treated tire chips on Compressive load, tensile load, axial strain, diametral strain, toughness index and post peak behaviour of the reference mix containing fly ash + 8% lime + 0.9% gypsum for a curing period varying from 7 to 180 days using three different curing methods. The results of this study revealed that the axial/diametral strain, axial/tensile load of reference mix mixed with dry tyre chip can be increased with the treatment provided on dry tyre chips. The axial/diametral strain, axial/tensile load, toughness index improves with the change in curing method and curing period. Potential use of this relatively new constructional material can be road pavement having light traffic....
Indigenous resources for natural and artificial mineral admixtures with high pozzolanic reactivity have been employed in many countries around the world. Extensive studies have been conducted for this purpose. With the use of agricultural waste residue, apart from improving properties of concrete, main benefits come from saving natural resources and energy, as well as protecting the environment by using these mineral admixtures (agroagricultural waste). The effective level of blending Portland cement (PC) in mortar or concrete with such mineral admixtures depends on many factors, such as the type of admixture and the cement replacement level. In the present paper two types of agroagricultural waste residue, namely, rice husk ash, bagasse ash and byproduct from thermal waste and fly ash were used. The above mentioned admixtures were thermally treated at a temperature of 650�°C. Characterizations of mineral admixtures were carried out by FTIR and XRD, and Microstructural properties were evaluated in concrete and mortar with partially replacement levels varying from 5% to 30%. Various tests such as water absorption, bulk volume of the specimen, dry weight of the specimen saturated mass, and coefficient of water absorption were concluded. The results showed that as the percentage of replacement level increases in the entire three admixtures studied, water absorption also increased....
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